Adaptive index mapping for modulation scheme settings

ABSTRACT

A node ( 100 ) of a cellular network selects a first modulation scheme setting for a first radio link to a first device ( 10 ′). The first modulation scheme setting is selected from a set of modulation scheme settings, each identified by at least one corresponding index. On the basis of a mapping of each of the indices to a corresponding set of transmission parameters, the node ( 100 ) identifies a first set of link parameters mapped to the index corresponding to the selected first modulation scheme setting. The node ( 100 ) then configures the first radio link according to the identified first set of link parameters. Further, the node ( 100 ) selects a second modulation scheme setting for a second radio link to a second device ( 10 ).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application claiming the benefit ofInternational Application No. PCT/EP2015/051942, filed Jan. 30,2015, theentire contents of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method of radio link control in acellular network and to correspondingly configured devices.

BACKGROUND OF THE INVENTION

In cellular networks, performance of a radio link to a device connectedto the cellular network may be optimized by adaptation of a modulationand coding scheme (MCS) utilized on the radio link. For example, in theLTE (Long Term Evolution) radio technology specified by 3GPP (3^(rd)Generation Partnership Project), modulation schemes ranging from QPSK(Quadrature Phase Shift Keying) to 256QAM (8^(th) order QuadratureAmplitude Modulation) may be selected depending on channel quality. Inthis way, a throughput in terms of a number of bits per transmitted datasymbol may be maximized on the given link.

Irrespective of a general trend to increased performance on the radiolink, also Machine Type Communication (MTC) is gaining increasingattention. In the case of MTC, autonomously operating devices such assensors or actuators, are connected via the cellular network andtypically operate without interaction of a user.

For MTC devices, low power consumption is an important aspect forensuring long battery life. To achieve such low power consumption,various measures may be considered. For example, in 3GPP TR 36.888V12.0.0 (2013-06), it is suggested to limit a transport block size ormodulation order on radio links to MTC devices. It is also mentionedthat BPSK (Binary Phase Shift Keying) could be utilized.

However, introducing a further modulation scheme into the existing LTEradio technology is a challenging task since the LTE radio technologywas designed to support modulation schemes ranging from QPSK up to256QAM, and a newly introduced modulation scheme should not adverselyaffect compatibility with existing LTE devices. For example, in the LTEradio technology, settings with respect to the modulation and codingscheme are identified through a 5-bit MCS index, referred to as I_(MCS),and a table in which modulation order and transport block size index arespecified for each MCS index value, as specified in 3GPP TS 36.213V12.4.0 (2014-12). Due to the limitation of the MCS index to 5 bits,also the size of the table is limited and cannot be extended beyond theexisting 32 entries. Further, also a complete replacement of the tableadds undesirable complexity because the existing version of the tablewould typically need to be maintained as well for compatibility reasons.

Accordingly, there is a need for techniques which allow for efficientlyincreasing the flexibility of a cellular network with respect to theselection of modulation schemes.

SUMMARY OF THE INVENTION

According to an embodiment of the invention, a method is provided.According to the method, a node of a cellular network, e.g., a basestation, selects a first modulation scheme setting for a first radiolink to a first device. The first modulation scheme setting is selectedfrom a set of modulation scheme settings, each identified by at leastone corresponding index. On the basis of a mapping of each of theindices to a corresponding set of transmission parameters, the nodeidentifies a first set of link parameters mapped to the indexcorresponding to the selected first modulation scheme setting. The nodethen configures the first radio link according to the identified firstset of link parameters. Further, the node selects a second modulationscheme setting for a second radio link to a second device. The secondmodulation scheme setting is based on a modulation scheme of lowercomplexity than the set of modulation scheme settings. For the secondradio link, the node re-assigns one of the indices to the selectedsecond modulation scheme setting and adapts the mapping with respect tothe set of link parameters mapped to re-assigned index. On the basis ofthe adapted mapping, the node identifies a second set of link parametersmapped to the re-assigned index. The node then configures the secondradio link according to the identified second set of link parameters.

Accordingly, the same index may be efficiently re-utilized foridentifying both link parameters for the modulation scheme settings fromthe set and for identifying link parameters for the additional secondmodulation scheme settings based on the lower complexity modulationscheme.

According to an embodiment, the at least one link parameter comprises amodulation order and/or a transport block size.

According to an embodiment, the set of modulation scheme settings isbased on QPSK and QAM. The second modulation scheme setting may be basedon BPSK, π/2 BPSK, or on GMSK (Gaussian Minimum Shift Keying).

According to an embodiment, the node indicates to the second device thatthe adapted mapping is applied on the second radio link. The seconddevice may then adapt its operation accordingly.

According to an embodiment, the node receives from the second device anindication of a device category of the second device. The node may thenselect the second modulation scheme setting in response to the devicecategory corresponding to a MTC category.

5

According to an embodiment, the node performs an analysis of parametersrelated to radio communication between the second device and thecellular network and selects the second modulation scheme setting on thebasis of the analysis.

10

The node may select the second modulation scheme setting atestablishment of the second radio link or may select the secondmodulation scheme setting during an ongoing connection via the secondradio link.

According to an embodiment, second modulation scheme setting is selectedfrom a set of multiple second modulation scheme settings and the nodere-assigns one of the indices to each of the multiple second modulationscheme settings. Accordingly, it is possible to support multipledifferent low complexity modulation schemes and/or different sets oflink parameters for such low complexity modulation scheme, e.g., withrespect to transport block size.

According to a further embodiment of the invention, a method isprovided. According to the method a device selects a first modulationscheme setting for a radio link to a cellular network, the firstmodulation scheme setting is selected from a set of modulation schemesettings, each identified by a corresponding index. On the basis of amapping of each of the indices to a corresponding set of linkparameters, the device identifying a first set of link parameters mappedto the index corresponding to the selected first modulation schemesetting. The device then configures the radio link according to theidentified first set of transmission parameters. Further, the deviceselects a second modulation scheme setting for the radio link, thesecond modulation scheme setting being based on a modulation scheme oflower complexity than the set of modulation scheme settings. The devicere-assigning one of the indices to the selected second modulation schemesetting and adapts the mapping with respect to the set of linkparameters mapped to the re-assigned index. On the basis of the adaptedmapping, the device identifies a second set of link parameters mapped tothe re-assigned index. The device then configures the second radio linkaccording to the identified second set of transmission parameters.

According to an embodiment, the at least one link parameter comprises amodulation order and/or a transport block size.

According to an embodiment, the set of modulation scheme settings isbased on QPSK and QAM. The second modulation scheme setting may be basedon BPSK, π/2 BPSK, or on GMSK.

According to an embodiment, the device selects the second modulationscheme setting in response to an indication from the cellular network.

The device may select the second modulation scheme setting atestablishment of the radio link or during an ongoing connection via theradio link.

According to an embodiment, the second modulation scheme setting isselected from a set of multiple second modulation scheme settings andthe device re-assigns one of the indices to each of the multiple secondmodulation scheme settings.

According to a further embodiment of the invention, a node for acellular network is provided. The node comprises at least one interfacefor controlling radio links to devices. Further, the node comprises atleast one processor. The at least one processor is configured to:

select a first modulation scheme setting for a first radio link to afirst device, the first modulation scheme setting being selected from aset of modulation scheme settings, each identified by at least onecorresponding index;

on the basis of a mapping of each of the indices to a corresponding setof transmission parameters, identify a first set of link parametersmapped to the index corresponding to the selected first modulationscheme setting;

configure the first radio link according to the identified first set oflink parameters;

select a second modulation scheme setting for a second radio link to asecond device, the second modulation scheme setting being based on amodulation scheme of lower complexity than the set of modulation schemesettings;

re-assign one of the indices to the selected second modulation schemesetting and adapt the mapping with respect to the set of link parametersmapped to re-assigned index;

on the basis of the adapted mapping, identify a second set of linkparameters mapped to the re-assigned index; and

configure the second radio link according to the identified second setof link parameters.

The at least one processor may be is configured to perform the steps ofthe above method performed by the node of the cellular network.

According to a further embodiment of the invention, a device isprovided. The device comprises a radio interface for connecting to acellular network. Further, the device comprises at least one processor.The at least one processor is configured to:

select a first modulation scheme setting for a radio link to a cellularnetwork, the first modulation scheme setting selected from a set ofmodulation scheme settings, each identified by a corresponding index;

on the basis of a mapping of each of the indices to a corresponding setof link parameters, identify a first set of link parameters mapped tothe index corresponding to the selected first modulation scheme setting;

configure the radio link according to the identified first set oftransmission parameters;

select a second modulation scheme setting for the radio link, the secondmodulation scheme setting being based on a modulation scheme of lowercomplexity than the set of modulation scheme settings;

re-assign one of the indices to the selected second modulation schemesetting and adapt the mapping with respect to the set of link parametersmapped to the re-assigned index;

on the basis of the adapted mapping, identify a second set of linkparameters mapped to the re-assigned index; and

configure the second radio link according to the identified second setof transmission parameters.

The at least one processor may be is configured to perform the steps ofthe above method performed by the device.

The above and further embodiments of the invention will now be describedin more detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a cellular network scenario accordingto an embodiment of the invention.

FIG. 2 shows an exemplary table for mapping indices of modulation schemesettings to link parameters as utilized in an embodiment of theinvention.

FIG. 3 shows a flowchart for illustrating processes according to anembodiment of the invention.

FIG. 4 shows a further cellular network scenario according to anembodiment of the invention.

FIG. 5 shows a flowchart for illustrating a method according to anembodiment of the invention.

FIG. 6 shows a flowchart for illustrating a further method according toan embodiment of the invention.

FIG. 7 schematically illustrates a processor based implementation of anetwork node according to an embodiment of the invention.

FIG. 8 schematically illustrates a processor based implementation of adevice according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, exemplary embodiments of the invention will bedescribed in more detail. It has to be understood that the followingdescription is given only for the purpose of illustrating the principlesof the invention and is not to be taken in a limiting sense. Rather, thescope of the invention is defined only by the appended claims and is notintended to be limited by the exemplary embodiments describedhereinafter.

The illustrated embodiments relate to control of radio links between acellular network and devices connected thereto. Radio connectivitybetween the devices and the cellular network is assumed to be providedby the LTE radio technology. However, it is to be understood that theillustrated concepts could also be applied in connection with otherradio technologies.

In the illustrated embodiments, it is assumed that at least twodifferent categories of devices may connect to the cellular network:normal UEs (UE: user equipment) and MTC UEs. The normal UEs may forexample correspond to mobile phones, tablet computers, or other kinds ofuser terminals. The MTC UEs may in turn correspond autonomouslyoperating devices, typically operated without interaction by a user,such as sensors, smart meters, wearable devices, or actuators. The MTCUEs typically also differ from the normal UEs with respect tocharacteristics of data traffic to or from the cellular network: Fornormal UEs high traffic volumes may be transferred depending on theusage behaviour of the user, with a higher traffic volume in a downlinkdirection from the cellular network to the UE than in an uplinkdirection from the UE to the cellular network. As compared to that, forMTC UEs typically lower traffic volumes are transferred in a sparsepattern. The data traffic of an MTC UE may also have a lower trafficvolume in the downlink direction than in the uplink direction. Ascompared to normal UEs, the sparse pattern and low volume of the datatraffic of an MTC UE typically also results in sizes of transferred datapackets which are smaller than for normal UEs. Further, also typicallocations of deployment of MTC UEs may differ from normal those ofnormal UEs. For example, an MTC UE may be deployed in a basement towhich penetration of radio signals from the cellular network is limited.

FIG. 1 schematically illustrates an exemplary cellular network scenario.More specifically, FIG. 1 shows a base station of the cellular network,in accordance with the assumed utilization of the LTE radio technologyin the following also referred to as eNB (“evolved Node B”), and devices10, 10′ connected via the eNB 100 to the cellular network. In theillustrated example, the device 10 corresponds to an MTC-UE, and thedevice 10′ corresponds to a normal UE. In the scenario of FIG. 1, afirst radio link is established between the normal UE 10′ and the eNB100, and a second radio link is established between the MTC UE 10 andthe eNB 100.

Due to the autonomous operation of MTC UEs, a lowered power consumptionis highly desirable to extend battery life. The concepts as furtherexplained in the following aim at enabling such lowered powerconsumption by supporting efficient operation of a power amplifier in aradio transceiver of the MTC UE. For this purpose, an LTE radio linkbetween an MTC UE and the cellular network may be enhanced to supportone or more modulation schemes of lower complexity, specifically lowerorder, than the modulation schemes conventionally supported on an LTEradio link, namely QPSK, 16QAM, 64QAM, and optionally 256QAM. Such lowercomplexity modulation scheme may for example be π/2 BPSK. Alternativelyor in addition, also BPSK or GMSK could be supported. Typically, thelower complexity modulation scheme modulates only one bit of data oneach transmitted data symbol. The lower complexity modulation scheme mayallow for operating the power amplifier in its linear region, and toachieve a low peak-to-average power ratio (PAPR) and low cubic metric(CM). Efficient operation of the power amplifier on the basis of suchlower complexity modulation scheme may also allow for a better qualityof the amplified radio signals and thus be beneficial with respect todeployments in environments with limited penetration of radio signals.The lower complexity modulation schemes may in particular be utilizedfor an uplink part of the LTE radio link, thereby reducing powerconsumption of a power amplifier in a transmit branch of the radiotransceiver. However, a reduction of power consumption may also beachieved by utilizing the lower complexity modulation schemes may in adownlink part of the LTE radio link, thereby reducing power consumptionof a power amplifier in a receive branch of the radio transceiver.

In the illustrated examples, the support of the lower complexitymodulation scheme is introduced by selective adaptation of a mechanismfor controlling settings with respect to a modulation scheme asspecified in 3GPP TS 36.213 V12.4.0. As defined in section 7.1.7 of 3GPPTS 36.213, for downlink transmission an MCS index, referred to asI_(MCS), and a table mapping values of the MCS index (0<I_(MCS) <32) tovalues of a modulation order Q_(m) and values of a TBS index settingsITBS is used to identify the modulation order and transport block sizeto be applied on the radio link. Here, the actual transport block sizeis determined as a function of the TBS index and a resource block size.As defined in section 8.6 of 3GPP TS 36.213, a similar mechanism isprovided for the uplink transmission direction. In FIG. 2, the table isillustrated for the case of supporting QPSK, 16QAM, and 64QAM modulationschemes, which are applicable for both the downlink transmissiondirection and the uplink transmission direction. A similar table alsoexits for the case of supporting QPSK, 16QAM, and 64QAM as modulationschemes.

As can be seen from the table of FIG. 2, the lowest 10 MCS indices areassigned to QPSK (modulation order Q_(m)=2). As a general rule, anachieved coding rate increases with the MCS index. To allow foradaptation to channel quality, selection of the MCS index for a givenradio link may depend on feedback from the UE in terms of a CQI (ChannelQuality Indicator). As a general rule, a higher CQI will result inselection of a higher MCS index.

To allow for utilizing a lower complexity modulation scheme, e.g., π/2BPSK, on the second radio link to the MTC UE 10, one or more of the MCSindices are re-assigned to the lower complexity modulation scheme.

For example, a group of the N lowest indices may be re-assigned to thelower complexity modulation scheme. The size of the group may be chosendepending on the number of different settings needed for the lowercomplexity modulation scheme. For example, if only one setting withrespect to TBS is needed, only the lowest MCS index would be re-assigned(N=1), or if two settings with respect to transport block size areneeded, the lowest two MCS indices would be re-assigned (N=2). At thesame time, the entries in of table which are mapped to the re-assignedindices are adapted. For example, the modulation order Q_(m) may be setto Q_(m)=1, and the TBS index may be lowered. This re-assignment andadaptation may be performed in a selective manner in response toidentifying the MTC UE 10 as belonging to the MTC category. Further, itshould be noted that this re-assignment and adaptation re-assignment andadaptation will typically be performed in a radio link specific manner.Accordingly, in the example as illustrated in FIG. 1, the re-assignmentand adaptation would be performed for the second radio link to the MTCUE 10, but not for the first radio link to the normal UE 10′.

FIG. 3 shows an exemplary process which may be applied by the eNB 100for controlling the selective re-assignment and adaptation of themapping defined by the table of FIG. 2.

At step 310, a UE connecting to the cellular network or alreadyconnected to the cellular network is categorized. For example, whenconnecting to the cellular network, the UE may send a preamble on aPhysical Random Access Channel (PRACH) to the eNB 100, and the preamblemay include an indication of UE category, allowing for identifyingwhether the UE corresponds to an MTC UE, or to some other UE category.

At step 320, the eNB 100 checks whether the UE corresponds to an MTC UE.If this is not the case, the process proceeds to step 330, as indicatedby branch “N”.

At step 330, the normal mapping as defined by the table of FIG. 2 isapplied for configuration of a radio link to the UE.

If at step 320 the eNB identifies the UE as corresponding to an MTC UE,the process proceeds to step 340, as indicated by branch “Y”. At step340, where the eNB 100 may decide whether the lower complexitymodulation scheme should be applied for this UE. This decision may forexample be based on an analysis of current or past data traffic of thisUE, or on analysis of parameters relating to such data traffic. Forexample, the UE may correspond to an MTC UE, but nonetheless frequentlytransfer higher volumes of data traffic and therefore benefit fromhigher order modulation schemes, and the eNB 100 may thus decide not toapply the lower complexity modulation scheme for this UE. The decisioncan also be based on the results from outer loop link adaptation (OLLA)at the eNB 100. Triggers and parameters to consider could be UE and/oreNB transmit power, packet error rate statistics, or the like. Togetherwith the decision to apply the lower complexity modulation scheme forthe UE, the eNB 100 may also decide that the higher order modulationschemes should be excluded from selection for this UE. Such decision mayfor example be taken in response to a corresponding indication from theUE and/or on the basis of the above-mentioned analysis of data trafficor parameters relating thereto.

If the eNB 100 decides not to apply the lower complexity modulationscheme, the process proceeds to step 330, as indicated by branch “N”.

If at step 340, the eNB 100 decides to apply the lower complexitymodulation scheme, the process proceeds to step 350, as indicated bybranch “Y”.

At step 350, the re-assignment of one or more indices is performed, andthe mapping adapted with respect to these indices is applied forconfiguration of a radio link to the UE. The eNB 100 may also indicatethe application of the adapted mapping to the UE, so that the UE mayadjust its operation accordingly, e.g., by applying a correspondinglyapplied mapping.

A process for selectively deciding whether to apply the adapted mappingor the normal mapping as explained in connection with FIG. 3 may notonly be applied when establishing the radio link to the UE, but alsoduring an ongoing connection with the UE. For example, switching betweenthe adapted mapping and the normal mapping could be triggered by changesin radio conditions or changes in the pattern of data traffic generatedby the UE.

FIG. 4 shows a further exemplary scenario, in which multiple UEs 10,10′, 10″, 10′″ have established radio links to the eNB 100. The UE 10 isagain assumed to be an MTC UE, while the UEs 10′, 10″, and 10′″ areassumed to be normal UEs.

As illustrated, the UEs 10, 10′, 10″, 10′″ are located at differentdistances from the eNB 100, which is assumed to cause variations in thechannel quality experienced by the respective UE 10, 10′, 10″, 10′″. Inthe illustrated scenario, the UEs 10 and 10′ are located closest to theeNB 100 and therefore experience the highest channel quality. The UE10′″, which is located farther away from the eNB 100, experiences alower channel quality than the UEs 10, 10′. The UE 10′″, which islocated still farther away from the eNB 100, experiences a lower channelquality than the UEs 10, 10′, and 10″.

In accordance with the channel quality dependent selection of modulationscheme settings from the table of FIG. 2, the radio link to the UE 10′may utilize a modulation scheme setting based on 64QAM, the radio linkto the UE 10″ may utilize a modulation scheme setting based on 16QAM,and the radio link to the UE 10′″ may utilize a modulation schemesetting based on QPSK, reflecting the decreasing channel quality.However, for the MTC UE 10, the low complexity modulation scheme may beselected based on the above-described processes, irrespective of thehigh channel quality experienced by the MTC UE 10. Such behaviour mayfor example be achieved by the MTC UE 10 indicating to the eNB 100 thatonly the low complexity modulation scheme should be selected for the MTCUE 10, i.e., by excluding the higher order modulation scheme settingsfrom being selected.

FIG. 5 shows a flowchart which illustrates a method which may be appliedby a node of a cellular network for controlling radio links to devices,e.g., by a base station, such as an eNB of the LTE radio technology. Ifa processor based implementation of the node is utilized, at least apart of the steps of the method may be performed and/or controlled byone or more processors of the node.

At step 510, the node selects a first modulation scheme setting for afirst radio link to a first device. The first modulation scheme settingis selected from a set of modulation scheme settings, each identified byat least one corresponding index. The modulation scheme settings may forexample be based on QPSK and QAM modulation schemes. An example of suchset of modulation scheme settings is given by the table of FIG. 2, inwhich 32 different modulation scheme settings are identified by the MCSindex.

At step 520, the node uses a mapping of each of the indices to acorresponding set of transmission parameters as a basis for identifyinga first set of link parameters mapped to the index corresponding to theselected first modulation scheme setting. As illustrated by theexemplary mapping defined by the table of FIG. 2, such link parametersmay for example include a modulation order and/or a transport blocksize.

At step 530, the node configures the first radio link according to theidentified first set of link parameters.

The first modulation scheme setting may be applied with respect to anuplink part of the first radio link and/or with respect to a downlinkpart of the first radio link.

At step 540, the node selects a second modulation scheme setting for asecond radio link to a second device. The second device may for examplebe a device of the MTC category. The second modulation scheme setting isbased on a modulation scheme of lower complexity than the set ofmodulation scheme settings. For example, the second modulation schemesetting may be based on BPSK, π/2 BPSK, or GMSK, while the set ofmodulation scheme settings may be based on QPSK and QAM.

The node may select the second modulation scheme setting atestablishment of the second radio link or during an ongoing connectionvia the second radio link.

In some implementations, the node may receive from the second device anindication of a device category of the second device. The node may thenselect the second modulation scheme setting in response to the devicecategory corresponding to the MTC category. Alternatively or inaddition, the node may also perform an analysis of parameters related toradio communication between the second device and the cellular networkand select the second modulation scheme on the basis of the analysis,e.g., as explained in connection with FIG. 3.

In some implementations, the second modulation scheme setting isselected from a set of multiple second modulation scheme settings andthe node re-assigns one of the indices to each of the multiple secondmodulation scheme settings. Each of these multiple modulation schemesettings may be based on the same modulation scheme having a lowercomplexity than the modulation scheme(s) on which the set of modulationscheme settings is based.

At step 550, the node re-assigns one of the indices to the selectedsecond modulation scheme setting and adapts the mapping with respect tothe set of link parameters mapped to re-assigned index. For example thismay involve mapping a lower modulation order and/or a lower transportblock size to the re-assigned index.

At step 560, uses the adapted mapping as a basis for identifying asecond set of link parameters mapped to the re-assigned index.

At step 570, the node configures the second radio link according to theidentified second set of link parameters. Further, the node may indicateto the second device that the adapted mapping is applied on the secondradio link, thereby allowing for the second device to adapt itsoperations accordingly.

The second modulation scheme setting may be applied with respect to anuplink part of the second radio link and/or with respect to a downlinkpart of the second radio link.

FIG. 6 shows a flowchart which illustrates a method which may be appliedby a device supporting radio connectivity to a cellular network, such asan MTC UE or other kind of UE. If a processor based implementation ofthe device is utilized, at least a part of the steps of the method maybe performed and/or controlled by one or more processors of the device.

At step 610, the device selects a first modulation scheme setting for aradio link to the cellular network. The first modulation scheme settingis selected from a set of modulation scheme settings, each identified byat least one corresponding index. The modulation scheme settings may forexample be based on QPSK and QAM modulation schemes. An example of suchset of modulation scheme settings is given by the table of FIG. 2, inwhich 32 different modulation scheme settings are identified by the MCSindex.

The device may select the first modulation scheme setting in response toan indication from the cellular network. For example, the cellularnetwork may indicate the index corresponding to the first modulationscheme setting to the device, e.g., in DCI (Downlink ControlInformation).

At step 620, the device uses a mapping of each of the indices to acorresponding set of transmission parameters as a basis for identifyinga first set of link parameters mapped to the index corresponding to theselected first modulation scheme setting. As illustrated by theexemplary mapping defined by the table of FIG. 2, such link parametersmay for example include a modulation order and/or a transport blocksize.

At step 630, the device configures the radio link according to theidentified first set of link parameters.

The first modulation scheme setting may be applied with respect to anuplink part of the radio link and/or with respect to a downlink part ofthe radio link.

At step 640, the device selects a second modulation scheme setting forthe radio link. The second modulation scheme setting is based on amodulation scheme of lower complexity than the set of modulation schemesettings. For example, the second modulation scheme setting may be basedon BPSK, π/2 BPSK, or GMSK, while the set of modulation scheme settingsmay be based on QPSK and QAM.

The device may select the second modulation scheme setting in responseto an indication from the cellular network. Further, the device mayreceive an indication from the cellular network that an adapted mappingis to be applied on the radio link. For example, in DCI the cellularnetwork may indicate the index corresponding to the second modulationscheme setting to the device and that the adapted mapping is to beapplied.

The device may select the second modulation scheme setting atestablishment of the radio link or during an ongoing connection via theradio link.

In some implementations, the second modulation scheme setting isselected from a set of multiple second modulation scheme settings andthe device re-assigns one of the indices to each of the multiple secondmodulation scheme settings. Each of these multiple modulation schemesettings may be based on the same modulation scheme having a lowercomplexity than the modulation scheme(s) on which the set of modulationscheme settings is based.

At step 650, the device re-assigns one of the indices to the selectedsecond modulation scheme setting and adapts the mapping with respect tothe set of link parameters mapped to re-assigned index. For example thismay involve mapping a lower modulation order and/or a lower transportblock size to the re-assigned index.

At step 660, the device uses the adapted mapping as a basis foridentifying a second set of link parameters mapped to the re-assignedindex.

At step 670, the node configures the radio link according to theidentified second set of link parameters.

The second modulation scheme setting may be applied with respect to anuplink part of the radio link and/or with respect to a downlink part ofthe radio link.

It is to be understood that the methods of FIGS. 5 and 6 may also becombined in a system which includes a network node operating accordingto the method of FIG. 5 and one or more devices operating according tothe method of FIG. 6.

FIG. 7 shows a block diagram for schematically illustrating a processorbased implementation of a network node which may be utilized forimplementing the above-described concepts. For example, the structuresas illustrated by FIG. 7 may be utilized to implement the eNB 100.

As illustrated, the network node includes an interface 110. For example,if the network node corresponds to a base station of a cellular network,such as the eNB 100, the interface 110 may correspond to a radiointerface through which devices may connect to the cellular network. Theinterface 110 may not only be utilized for establishing radio links tothe devices, but also for controlling such radio links.

Further, the network node is provided with one or more processors 140and a memory 150. The interface 110 and the memory 150 are coupled tothe processor(s) 140, e.g., using one or more internal bus systems ofthe network node.

The memory 150 includes program code modules 160, 170, 180 with programcode to be executed by the processor(s) 140. In the illustrated example,these program code modules include a link adaptation module 160, anindex mapping module 170, and a signaling module 180.

The link adaptation module 160 may implement the above-describedfunctionalities of configuring radio links by applying link parametersidentified by an index. This may also involve selecting an appropriateindex depending on channel quality or other criteria.

The index mapping module 170 may implement the above-describedfunctionalities of re-assigning one or more indices to a lowercomplexity modulation scheme and adapting link parameters mappedthereto.

The signaling module 180 may implement the above-describedfunctionalities of receiving indications from devices, e.g., concerningdevice category or preferred usage of a lower complexity modulationscheme, and the above-described functionalities of sending indicationsto devices, e.g., concerning the selected modulation scheme setting orwhether the adapted mapping is applied.

It is to be understood that the structures as illustrated in FIG. 7 aremerely exemplary and that the network node may also include otherelements which have not been illustrated, e.g., structures or programcode modules for implementing known functionalities of an eNB or othernetwork node.

FIG. 8 shows a block diagram for schematically illustrating a processorbased implementation of a device which may be utilized for implementingthe above-described concepts. For example, the structures as illustratedby FIG. 8 may be utilized to implement the MTC UE 10.

As illustrated, the device includes a radio interface 210, e.g., a radiointerface supporting the LTE radio technology. Through the interface210, the device may connect to a cellular network. To improve powerefficiency, the interface 210 may include a transceiver equipped with ahigh efficiency power amplifier.

Further, the device is provided with one or more processors 240 and amemory 250. The interface 210 and the memory 250 are coupled to theprocessor(s) 240, e.g., using one or more internal bus systems of thedevice.

The memory 250 includes program code modules 260, 270, 280 with programcode to be executed by the processor(s) 240. In the illustrated example,these program code modules include a link configuration module 260, anindex mapping module 270, and a signaling module 280.

The link configuration module 260 may implement the above-describedfunctionalities of configuring a radio link from the device to thecellular network. This involves by applying link parameters identifiedby an index.

The index mapping module 270 may implement the above-describedfunctionalities of re-assigning one or more indices to a lowercomplexity modulation scheme and adapting link parameters mappedthereto.

The signaling module 280 may implement the above-describedfunctionalities of sending indications to the cellular network, e.g.,concerning device category or preferred usage of a lower complexitymodulation scheme, and the above-described functionalities of receivingindications from the cellular network, e.g., concerning the selectedmodulation scheme setting or whether the adapted mapping is applied.

It is to be understood that the structures as illustrated in FIG. 8 aremerely exemplary and that the device may also include other elementswhich have not been illustrated, e.g., structures or program codemodules for implementing known functionalities of an MTC UE or otherkind of UE.

As can be seen, the concepts as explained above allow for efficientlycontrolling configuration of radio links. In particular, lowercomplexity modulation schemes may be efficiently supported along one ormore other modulation schemes. In this way, low power consumption forMTC UEs and similar devices may be achieved.

It is to be understood that the concepts as explained above aresusceptible to various modifications. For example, the concepts could beapplied in various kinds of devices and in connection with various kindsof radio technologies. Further, it is to be understood that the conceptsmay be applied by providing suitably configured software to be executedby a processor of a node of a cellular network or by a processor of adevice supporting connectivity to a cellular network.

1. A method, comprising: a node of a cellular network selecting a firstmodulation scheme setting for a first radio link to a first device, thefirst modulation scheme setting being selected from a set of modulationscheme settings, each identified by at least one corresponding index; onthe basis of a mapping of each of the indices to a corresponding set oftransmission parameters, the node identifying a first set of linkparameters mapped to the index corresponding to the selected firstmodulation scheme setting; the node configuring the first radio linkaccording to the identified first set of link parameters; the nodeselecting a second modulation scheme setting for a second radio link toa second device, the second modulation scheme setting being based on amodulation scheme of lower complexity than the set of modulation schemesettings; the node re-assigning one of the indices to the selectedsecond modulation scheme setting and adapting the mapping with respectto the set of link parameters mapped to re-assigned index; on the basisof the adapted mapping, the node identifying a second set of linkparameters mapped to the re-assigned index; and the node configuring thesecond radio link according to the identified second set of linkparameters.
 2. The method according to claim 1, wherein the at least onelink parameter comprises a modulation order.
 3. The method according toclaim 1, wherein the at least one link parameter comprises a transportblock size.
 4. The method according to claim 1, wherein the set ofmodulation scheme settings is based on Quadrature Phase Shift Keying andQuadrature Amplitude Modulation.
 5. The method according to claim 1,wherein the second modulation scheme setting is based on Binary PhaseShift Keying, n/2 Binary Phase Shift Keying, or on Gaussian MinimumShift Keying.
 6. The method according to claim 1, comprising: the nodeindicating to the second device that the adapted mapping is applied onthe second radio link.
 7. The method according to claim 1, comprising:the node receiving from the second device an indication of a devicecategory of the second device; and the node selecting the secondmodulation scheme setting in response to the device categorycorresponding to a machine-type communication category.
 8. The methodaccording to claim 1, comprising: the node performing an analysis ofparameters related to radio communication between the second device andthe cellular network; and on the basis of the analysis, the nodeselecting the second modulation scheme.
 9. The method according to claim1, comprising: the node selecting the second modulation scheme settingat establishment of the second radio link.
 10. The method according toclaim 1, comprising: the node selecting the second modulation schemesetting during an ongoing connection via the second radio link.
 11. Themethod according to claim 1, wherein the second modulation schemesetting is selected from a set of multiple second modulation schemesettings and the node re-assigns one of the indices to each of themultiple second modulation scheme settings.
 12. A method, comprising: adevice selecting a first modulation scheme setting for a radio link to acellular network, the first modulation scheme being setting selectedfrom a set of modulation scheme settings, each identified by acorresponding index; on the basis of a mapping of each of the indices toa corresponding set of link parameters, the device identifying a firstset of link parameters mapped to the index corresponding to the selectedfirst modulation scheme setting; the device configuring the radio linkaccording to the identified first set of transmission parameters; thedevice selecting a second modulation scheme setting for the radio link,the second modulation scheme setting being based on a modulation schemeof lower complexity than the set of modulation scheme settings; thedevice re-assigning one of the indices to the selected second modulationscheme setting and adapting the mapping with respect to the set of linkparameters mapped to the re-assigned index; on the basis of the adaptedmapping, the device identifying a second set of link parameters mappedto the re-assigned index; and the device configuring the second radiolink according to the identified second set of transmission parameters.13. The method according to claim 12, wherein the at least one linkparameter comprises a modulation order.
 14. The method according toclaim 12, wherein the at least one link parameter comprises a transportblock size.
 15. The method according to claim 12, wherein the set ofmodulation scheme settings is based on Quadrature Phase Shift Keying andQuadrature Amplitude Modulation.
 16. The method according to claim 12,wherein the second modulation scheme setting is based on Binary PhaseShift Keying, π/2 Binary Phase Shift Keying or on Gaussian Minimum ShiftKeying.
 17. The method according to claim 12, comprising: the deviceselecting the second modulation scheme setting in response to anindication from the cellular network.
 18. The method according to claim12, comprising: the device selecting the second modulation schemesetting at establishment of the radio link.
 19. The method according toclaim 12, comprising: p1 the device selecting the second modulationscheme setting during an ongoing connection via the radio link.
 20. Themethod according to claim 12, wherein the second modulation schemesetting is selected from a set of multiple second modulation schemesettings and the device re-assigns one of the indices to each of themultiple second modulation scheme settings.
 21. A node for a cellularnetwork, the node comprising: at least one interface for controllingradio links to devices; and at least one processor, the at least oneprocessor being configured to: select a first modulation scheme settingfor a first radio link to a first device, the first modulation schemesetting being selected from a set of modulation scheme settings, eachidentified by at least one corresponding index; on the basis of amapping of each of the indices to a corresponding set of transmissionparameters, identify a first set of link parameters mapped to the indexcorresponding to the selected first modulation scheme setting; configurethe first radio link according to the identified first set of linkparameters; select a second modulation scheme setting for a second radiolink to a second device, the second modulation scheme setting beingbased on a modulation scheme of lower complexity than the set ofmodulation scheme settings; re-assign one of the indices to the selectedsecond modulation scheme setting and adapt the mapping with respect tothe set of link parameters mapped to re-assigned index; on the basis ofthe adapted mapping, identify a second set of link parameters mapped tothe re-assigned index; and p1 configure the second radio link accordingto the identified second set of link parameters.
 22. The node accordingto claim 21, wherein the at least one processor is configured to performthe steps of the method comprising, a node of a cellular networkselecting a first modulation scheme setting for a first radio link to afirst device, the first modulation scheme setting being selected from aset of modulation scheme setting, each identified by at least onecorresponding index; on the basis of a mapping of each of the indices toa corresponding set of transmission parameters, the node identifying afirst set of link parameters mapped to the index corresponding to theselected first modulation scheme setting; the node configuring the firstradio link according to the identified first set of link parameters; thenode selecting a second modulation scheme setting for a second radiolink to a second device, the second modulation scheme setting beingbased on a modulation scheme of lower complexity than the set ofmodulation scheme settings; the node re-assigning one of the indices tothe selected second modulation scheme setting and adapting the mappingwith respect to the set of link parameters mapped to re-assigned index;on the basis of the adapted mapping, the node identifying a second setof link parameters mapped to the re-assigned index; and the nodeconfiguring the second radio link according to the identified second setof link parameters.
 23. A device, comprising: a radio interface forconnecting to a cellular network; and at least one processor, the atleast one processor being configured to: select a first modulationscheme setting for a radio link to a cellular network, the firstmodulation scheme setting selected from a set of modulation schemesettings, each identified by a corresponding index; on the basis of amapping of each of the indices to a corresponding set of linkparameters, identify a first set of link parameters mapped to the indexcorresponding to the selected first modulation scheme setting; configurethe radio link according to the identified first set of transmissionparameters; select a second modulation scheme setting for the radiolink, the second modulation scheme setting being based on a modulationscheme of lower complexity than the set of modulation scheme settings;re-assign one of the indices to the selected second modulation schemesetting and adapt the mapping with respect to the set of link parametersmapped to the re-assigned index; on the basis of the adapted mapping,identify a second set of link parameters mapped to the re-assignedindex; and configure the second radio link according to the identifiedsecond set of transmission parameters.
 24. The device according to claim23, wherein the at least one processor is configured to perform thesteps of the method comprising, a device selecting a first modulationscheme setting for a radio link to a cellular network, the firstmodulation scheme being setting selected from a set of modulation schemesettings, each identified by a corresponding index; on the basis of amapping of each of the indices to a corresponding set of linkparameters, the device identifying a first set of link parameters mappedto the index corresponding to the selected first modulation schemesetting; the device configuring the radio link according to theidentified first set of transmission parameters; the device selecting asecond modulation scheme setting for the radio link, the secondmodulation scheme setting being based on a modulation scheme of lowercomplexity than the set of modulation scheme settings; the devicere-assigning one of the indices to the selected second modulation schemesetting and adapting the mapping with respect to the set of linkparameters mapped to the reassigned index; on the basis of the adaptedmapping, the device identifying a second set of link parameters mappedto the re-assigned index; and the device configuring the second radiolink according to the identified second set of transmission parameters.